Known methods for obtaining semiconductors having one conductivity type by low-temperature steps include ion implantation and sputtering. However, ion implantation does not provides high productivity. Sputtering has the advantages that the process can be performed at low temperatures below 200.degree. C. and that high productivity can be obtained. However, the electrical characteristics of the formed semiconductor film are so poor that this method cannot be put into practical use. For example, the electrical characteristics of a device fabricated using a semiconductor film formed by sputtering are low.
Two known methods are available to obtain a p- or n-type semiconductor film, e.g., a silicon film of one conductivity type, by the prior art sputtering. In one known method, a target consisting of a single crystal of silicon which is doped with an impurity to impact one conductivity type to the crystal is used. A sputtering process is carried out, using this target within an atmosphere consisting only of argon. In the other known method, a target consisting of a single crystal of silicon which is not doped with an impurity imparting p or n type is employed. A sputtering process is effected, using this target within an atmosphere of argon to which a reactant gas, e.g., phosphine, containing an element imparting one conductivity type is added. However, it is impossible to form a semiconductor film having one conductivity type, i.e., either p or n type, and an electrical conductivity exceeding 10.sup.-5 (.OMEGA..cm).sup.-1 by the prior art techniques, because the impurity imparting a conductivity type, either p or n, does not form a donor or acceptor.